When the hyperplane arrangement is degenerate, i.e. not in general position, the number of distinct cells can be checked against the formula of Alexanderson and Wetzel (1981).
polycount(A, b, maxints = 10)
number of distinct cells
is a n by m matrix of hyperplane slope coefficients
is an n vector of hyperplane intercept coefficients
is maximum number of lines allowed to cross at the same vertex
Alexanderson, G.L and J.E. Wetzel, (1981) Arrangements of planes in space, Discrete Math, 34, 219--240.